-LRB- CNN -RRB- -- Two health care workers went to the emergency room with flu-like symptoms after coming into contact with a patient confirmed to have Middle East Respiratory Syndrome , or MERS , officials said Tuesday .

The Florida patient represents the second confirmed case of MERS brought into the United States , the Centers for Disease Control and Prevention said Monday . MERS is a mysterious virus that can be fatal , and was first found in the Arabian Peninsula in 2012 .

One health care worker in Orlando began showing symptoms 72 hours after exposure to the MERS patient but did not meet criteria for admission and was sent home , said Dr. Antonio Crespo , an infectious disease specialist at Dr. P. Phillips Hospital , where the MERS patient is being treated . The health care worker will be monitored and seems to be improving , Crespo said .

The other one , whose symptoms began 24 hours after exposure , was admitted to the same hospital , officials said Tuesday at a press conference .

`` We 're just waiting for the results from the testing that was done yesterday to decide about discharge , '' Crespo said .

At-risk workers at home

The two health care workers are among 20 in the Orlando area who may have been exposed to the MERS patient , and they are being tested for the virus , officials said . They were all notified and told to stay home and not work for 14 days , Crespo said . They also should monitor their temperatures and check for possible symptoms such as a cough , sore throat and fever .

Five health team members who may be at risk have been identified at Orlando Regional Medical Center and 15 at Dr. P. Phillips Hospital , Crespo said .

They were all evaluated for signs and symptoms that would be consistent for MERS . Samples were sent to the state lab for testing , said Dr. Ken Michaels , medical director for occupational health at Orlando Health .

`` I 'm glad to report that I 've spoken to most of these team members today . They all report that they 're doing great , '' Michaels said .

On the 14th day , everyone involved will be brought back for further testing . Once medically cleared , they can return to work , officials said .

Initial testing should be back within the next day or two , Michaels said .

MERS : 5 things to know

Two confirmed U.S. cases

The confirmed MERS patient visited Orlando Regional Medical Center on May 5 , accompanying another person who was having a medical procedure , officials said .

`` I think the risk is negligible to those in the waiting room or the radiology area at -LRB- Orlando Regional Medical Center -RRB- , '' said Dr. Kevin Sherin of the Florida Department of Health in Orange County .

The MERS patient was admitted to Dr. P. Phillips Hospital on May 9 .

`` Before the patient came to the hospital , he was not having a cough , '' Crespo said . `` He was not having respiratory symptoms . So we believe that that makes less risk of transmission to other potential contacts . ''

Officials from the CDC and the Florida Department of Health are investigating the MERS case .

During a White House briefing Tuesday , press secretary Jay Carney said President Barack Obama had been briefed on the MERS situation in the United States and that the CDC is taking the lead .

The first U.S. case was reported this month in Indiana . That patient was released from a hospital Friday into home isolation , according to state health officials .

The Indiana patient was an American health care provider who had been working in Saudi Arabia and was on a planned visit to Indiana to see his family .

The Florida patient is also a health care provider who lives and works in Saudi Arabia , said Dr. Anne Schuchat , assistant surgeon general with the U.S. Public Health Service and director of the CDC 's National Center for Immunization and Respiratory Diseases . She said that he is not a U.S. citizen and that the Florida case is not linked to the Indiana one .

The U.S. Transportation Security Administration will post CDC advisories at more than 20 U.S. airports to alert travelers about the virus .

Although there are no recommendations to change travel plans , the signs will advise travelers to the Arabian Peninsula to avoid contact with sick people and wash their hands often . They should contact a doctor if they develop symptoms such as fever , shortness of breath and coughing , the CDC said .

`` We think it 's really critical to avoid overreacting in the community but also avoid under-reacting in the health care environment , '' Schuchat told CNN . `` The reason for the signage is so that we can promptly identify potential cases so that they can be separated from other people . ''

Can SARS lessons prevent a MERS virus outbreak ?

What is MERS ?

As of Friday , there have been 538 cases of MERS in 17 countries , including 145 deaths , according to the World Health Organization , Schuchat said .

The virus is also known as MERS-CoV since it is a coronavirus , the same group of viruses as the common cold . It attacks the respiratory system , according to the CDC . Symptoms can lead to pneumonia or kidney failure .

There is no vaccine or special treatment for MERS . Doctors said they believe the Indiana patient 's quick diagnosis and care dramatically increased his chances for getting better .

The `` risk to the general public remains very low , '' Schuchat said . In some countries , the virus has spread from person to person , but only in close contact , such as a person who was caring for an ill person .

`` This virus has not shown the ability to spread easily from person to person in community settings , '' she said .

Out of `` an abundance of caution , '' the CDC has been contacting people who were passengers on the same flights as the two patients with confirmed MERS , Schuchat said .

No cases of MERS have been diagnosed as a result of transmission on a plane , the CDC 's Dr. Marty Cetron said .

The 44-year-old Florida patient traveled on May 1 from Jeddah , Saudi Arabia , to London , then from London to Boston , Boston to Atlanta , and finally Atlanta to Orlando .

The man began feeling unwell on the flight from Jeddah , with symptoms including `` fever , chills and a slight cough , '' Schuchat said .

Family members of the patient have been tested as well , Crespo said .

`` The patient has been doing very well , '' Crespo said . The patient had a low-grade fever of 100.2 on Monday night but has a minimal cough , and he is `` in great spirits . ''

MERS mystery : Virus found in camels

CNN 's Miriam Falco , Elizabeth Cohen , Jen Christensen , and Athena Jones contributed to this report .

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NEW : TSA will put up advisories about MERS in airports

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Two cases have been confirmed in the U.S.

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At least 20 health care workers told to not come to work

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They can return to work after 14 days if medically cleared